Periodic registration mechanism for duplicators



Nov. 8, 1966 G. J. ZAHRADNIK ET AL 3,283,710

PERIODIC REGISTRATION MECHANISM FOR DUPLICATORS Filed May 25, 1964 4Sheets-Sheet l Fla 1 INVENTORS George JZaftradrzik and Fred 5. Golden 9Fin. 2

dtlys Nov. 8, 1966 3,283,710

PERIODIC REGISTRATION MECHANISM FOR DUPLICATORS Filed May 25, 1964 G. J.ZAHRADNIK ET AL 4 Sheets-Sheet 2 .WHHU

m mwg J. zahmg k Nov. 8, 1966 G. J. ZAHRADNIK ET AL 3,283,710 7 PERIODICREGISTRATION MECHANISM FOR DUPLICATORS Filed May 25, 1964 4 Sheets-Sheets /N VEN 7025 George J. Zahradnlk and Fred 5 G0 .aen

NOV. 8, 1966 ZAHRADNIK ET AL 3,283,710

PERIODIC REGISTRATION MECHANISM FOR DUPLIGATORS 4 Sheets-Sheet 4 FiledMay 25, 1964 FIG. 15

FIG. 13

United States Patent 3,283,710 PERIODIC REGISTRATION MECHANISM FORDUPLICATOR George J. Zahradnik, North Riverside, and Fred S.

Golden, Chicago, Ill., assignors to A. B. Dick Company, Niles, 11]., acorporation of Illinois Filed May 25, 1964, Ser. No. 370,028

- 12 Claims. (Cl. 101-248) This invention relates particularly tostencil duplicators but is also applicable to other types of printingpresses or the like.

One object of the present invention is to provide a new and improvedduplicator in which the impression cylinder is periodically brought intoexact registration with the adjacent main cylinder, at one point in thecycle of the main cylinder, and then is allowed to float relative to themain cylinder so that the impression cylinder will be frictionallydriven by the main cylinder. The momentary registration of theimpression cylinder makes it possible to insure exact registrationbetween the copy sheets and the main cylinder. The impression cylinderis frictionally driven while the copy sheets are being printed so as toobviate any tendency toward slippage between the impression cylinder andthe main cylinder. In the case of a stencil duplicator, such tendencytoward slippage may cause stretching or wrinkling of the stencil.

A further object is to provide a new and improved duplicator in whichthe impression cylinder is driven by a registration mechanism whichprovides a positive drive at one point in the cycle of the maincylinder, the mechanism being adapted to introduce a variable amount ofslack into the drive during the remainder of the cycle. Because of thisslack, the impression cylinder is actually propelled by the frictionaldriving action of the main cylinder while the copy sheets are beingprinted.

It is a further object to provide a new and improved duplicator in whichthe successive copy sheets are carried between the main cylinder and theimpression cylinder by a gripper bar which is supported and advanced bya pair of endless chains, the impression cylinder being formed with anotch for receiving the gripper bar and being driven by a registrationmechanism which momentarily synchronizes the impression cylinder withthe gripper chains, so that the notch will register with the gripperbar. After the gripper bar has passed the impression cylinder, slack isintroduced into the drive for the impression cylinder so that it will'be frictionally driven by the main cylinder during the actual printingoperation. It this way, the impression cylinder will not exert any dragor any pull on the main cylinder, so that there will be no tendencyeither to stretch or wrinkle the stencil or other printing sheet on themain cylinder.

In general, it is an object of the present invention to provide aregistration mechanism which periodically registers or synchronizes thecylinder or other printing member with a positive drive, and thenintroduces more or less slack into the drive so that the cylinder canrun either slightly ahead or slightly behind its positive drive.

A more specific object is to provide a registration mechanism in whichthe slack in the drive is changed by the rotation of a cam or eccentricwhich has a cycle corresponding to the cycle of the main cylinder orother printing member with which the impression cylinder is to beregistered.

Another object is to provide such a registration mechanism in which thevariable slack is produced between a pair of eccentric cams, which aredifferent in phase by 180, and a pair of arms on a forked drive member.

A further object is to provide such a registration mechanism in whichthe eccentrices or cams are rotated by a planetary gear which is carriedby the impression cylinder and is driven 'by a stationary piniondisposed along the aXis of thecylinder. In one preferred arrangement,the planetary gear is rotated at one-half the rotary speed of theimpression cylinder, so that the impression cylinder is registered oncefor every two revolutions thereof. This arrangement is adapted for usewith a machine in which the diameter of the impression cylinder isonehalf the diameter of the main cylinder, so that the main cylinderrotates at one-half the rotary speed of the impression cylinder.

Another object is to provide various modified registratio-n mechanismsin which the variable slack is produced between a drive pin and atapered notch in a forked drive member which is movable toward and awayfrom the pin.

A further object is to provide such registration mechanisms in which theforked drive member is moved into and out of engagement with the pin bya cam or eccentric.

It is a further object to provide such registration mechanisms in whichthe cam or eccentric is provided with a separate drive gear, sprocket orthe like.

Further objects and advantages of the present invention will appear fromthe following description, taken with the accompanying drawings, inwhich:

FIG. 1 is a diagrammatic elevational view showing a duplicating machinewhich is equipped with a registration mechanism for periodicallyregistering the impression cylinder with a gripper bar carried byendless drive chains.

FIG. 2 is an enlarged elevational section taken through the impressioncylinder and the gripper bar to show various details of the registrationmechanism, the view being taken generally along the line 22 in FIG. 3.

FIG. 3 is a fragmentary enlarged sectional plan view taken generallyalong the broken lines 3-3 in FIG. 1.

FIG. 4 is a sectional view taken generally along the line 44 in FIG. 3.

FIG. 5 is a diagrammatic elevational section showing the manner in whichthe main cylinder is driven by one of the gripper chains, the view beingtaken generally along the line 5-5 in FIG. 3.

FIG. 6 is a fragmentary enlarged section taken generally along the line6-6 in FIG. 5.

FIG. 7 is a fragmentary plan view showing the manner in which thegripper bar is attached to the gripper chains.

FIG. 8 is a diagrammatic elevational section showing a modifiedregistration mechanism, the view being taken generally along the line 88in FIG. 9.

FIG. 9 is a fragmentary sectional plan view taken generally along theline 9-9 in FIG. 8.

FIG. 10 is a view similar to FIG. 8 but showing another modifiedregistration mechanism, the view being taken generally along the line1010 in FIG. 11.

FIG. 11 is a fragmentary section taken generally along the line 11111 inFIG. 10.

FIG. 12 is a view similar to FIG. 8 but showing still another modifiedconstruction, the view being taken generally along the line 1212 in FIG.13.

FIG. 13 is a fragmentary section taken generally along the line 13-13 inFIG. 12.

FIG. 14 is a sectional view similar to FIG. 8 but showing still anothermodified registration mechanism, the view being taken generally alongthe line 14-14 in FIG. 15.

FIG. 15 is a fragmentary section taken generally along the line 15--15in FIG. 14.

As already indicated, the invention is illustrated in FIG. 1 inconnection with a duplicator or printing press 20, which preferably is astencil-type duplicator. As shown, the duplicator 20 comprises a main.cylinder 22 which is adapted to hold a stencil or other member fromwhich a printed impression can be made on paper or other copy sheets. Animpression cylinder 24 is provided 3 to press the copy sheets againstthe main cylinder or drum 22.

A feed mechanism 26 is preferably provided to feed the successive copysheets 28 between the main cylinder 22 and the impression cylinder 24.In this case, a stack 30 of the copy sheets 28 is supported on a feedtable 32. A rotatable feed roller 34 is adapted to engage the top of thestack 30 so as to feed the topmost sheet therefrom, into a chute oropening 36 between upper and lower guide plates 38 and 40. Cornerseparators 42 may be employed adjacent the rear comers of the stack 30to insure that only a single sheet will be fed from the top of the stackby the roller 34. g

The guide plates 38 and 40 direct each sheet between upper and lowerforwarding rollers 44 and 46 which are rotated in timed relation to thefeed roller 34 so as to propel the sheets toward the main cylinder 22.

In the illustrated duplicating machine 20, each of the sheets is takenfrom the forwarding rollers 44 and 46 and is carried between thecylinders 22 and 24 by a set of grippers or clamping fingers 48 whichare movably mounted on a gripper bar and are adapted to clamp theleading edge of each copy sheet against the bar 50. As shown, thegripper bar Si} is carried and propelled by a pair of endless gripperchains 52 which are strung around sprockets 54 and 56. However, it willbe understood that the invention is also applicable to machines in whichthe grippers are carried by the impression cylinder. One of theillustrated sprockets, preferably the sprocket 54, is continuouslydriven so that the chains will be advanced at a constant speedcorresponding to the surface speed of the main cylinder 22. In fact, themain cylinder 22 is preferably fitted with a sprocket 58 (FIGS. and 6)which meshes with and is driven by one of the gripper chains 52.

Just beyond the forwarding rollers 4-4 and 46, the grippers 48 passunder a guide plate or member 60 which guides the leading end of eachpaper sheet into the grippers, which are opened at this point by a cam,not shown, in the usual manner. The gripper bar 50 travels in agenerally horizontal direction between the two sprockets 54 and 56 sothat the sheets are carried horizontally between cylinders 22 and 24-.The grippers 48 insure that each sheet is precisely registered with themain cylinder 22, so that the imprint of the stencil will be accuratelylocated on the sheet. The grippers 48 continue to propel and control thesheets after they pass between the cylinders 22 and 24. Thus, thegrippers overcome the tendency of the sheets to stick to the inkedstencil on the main cylinder 22. As the grippers pass around thesprocket 56 they are opened by another cam, not shown, in the usualmanner, so that each sheet is ejected from the grippers and is directedinto a receiving tray 62. If desired, a delivery system or conveyor maybe employed to carry the sheets to the receiving tray 62.

A longitudinal notch or groove 64 is formed in the impression cylinder24 in order that the gripper bar 50 may pass between the main cylinder22 and the impression cylinder 24 without interference. As shown to bestadvantage in FIG. 2, the gripper bar 50 is adapted to be received in thenotch 64.

A registration mechanism 66 is provided to drive the impression cylinder24 in such a manner that the notch 64 will register with the gripper bar50. Of course, this in itself could be achieved simply by providing apositive gear or chain drive for the impression cylinder 24, so as torotate the impression cylinder in timed relation to the gripper chains52. However, the present registering mechanism 66 operates in aperiodical manner so as to provide a positive drive at only one point inthe cycle of the mechanism, when the gripper bar 50 is passing theimpression cylinder 24 and is to be received in the notch 64. After thegripper bar 50 is past the impression cylinder 24, the registrationmechanism 66 introduces a substantial slack or free play into the drivefor the impression cylinder 24 so that the cylinder is actuallyfrictionally driven by the main cylinder 22 during the printingoperation, in which one of the copy sheets is being pressed between themain cylinder and the impression cylinder. The impositiveness of thedrive and the resulting frictional propulsion of the impression cylinder24 obviates any tendency of the impression cylinder to exert a drag orpull upon the stencil on the main cylinder 22. If the impressioncylinder 24 were positively driven at all times, its surface would tendto run slightly faster or slower than the surface of the stencil on themain cylinder 22, in most cases, due to slight variations in theeffective printing radius of the stencil. The printing radius isaffected by the thickness of the stencil, the thickness of the ink pador the like under the stencil, and the initial tension in the stencil.If the printing radius is slightly greater than nominal value, thesurface speed of the stencil is greater than normal. In this case, theimpression cylinder 24 would run behind the stencil and would tend toexert a drag on the stencil so that the impression cylinder would tendto stretch the stencil. In extreme cases, actual slippage might resultbetween the cylinders. If the printing radius is slightly smaller thanthe nominal value, the stencil runs slower than the normal speed. Inthis case, the impression cylinder, if positively driven, would tend toexert a pull on the stencil, so that there would be a tendency for theimpression roller to wrinkle the stencil. The registration mechanism 66obviates these difficulties by providing for the frictional propulsionof the impression roller 24 during the printing operation, so that theimpression roller runs at the exact speed of the stencil. Theregistration mechanism affords suificient slack in the drive to theimpression cylinder to enable the impression roller to run either aheadof or behind the drive so as to compensate for the usual variations inthe printing radius. Thus, the registration mechanism 66 provides adrive which is positive at one point in the cycle and is impositive inthe following portions of the cycle during which the actual printmgoperation is carried out.

The details of the registration mechanism 66 are shown to best advantagein FIGS. 2, 3 and 4. In accordance with the usual practice, theimpression cylinder 24 is movably mounted so that it may be separatedfrom the main cylinder 22 when paper sheets are not being fed betweenthe cylinders. This separation prevents the imprint of the stencil frombeing applied to the impression cylinder. It will be seen that thecylinder 24 is supported by a pair of generally horizontal arms 68 whichare swingable about a shaft 7%. This is the same shaft on which thesprockets 54 for the gripper chains 52 are mounted. The arms 68 arebiased upwardly or counterclockwise by springs 72 which are effective toapply pressure between the impression cylinder 24 and the main cylinder22 during the printing operation. The impression cylinder 24 isrotatably supported between the outer ends of the arms 66. One of thearms 68 and the rotatable support for one end of the cylinder 24 isshown in detail in FIG. 3. It will be seen that a shaft or trunnion 74is secured to the arm 63 and projects inwardly therefrom. The cylinder24 is rotatably supported by a ball bearing 76, or other antifrictionhearing, which is mounted between the shaft 74 and an end plate or disc'78 secured within the end of the cylinder. A second ball bearing 89 ismounted between the shaft '74 and a plate 82 which is connected to theend plate 78 by pillars or pins 84.

In this case, the drive for the impression cylinder 24 utilizes a chain86 which is strung around sprockets 88 and 90, and also a toothlessidler sprocket 9 2. The sprocket 88 is secured to the shaft 7% and thusrotates with the sprockets 54 for the gripper chains 52. The sprocket 90is rotatably mounted on the shaft 74. As shown to best advantage in FIG.4, the idler sprocket 92 outer end of an arm 96, swingable about theshaft '70 adjacent the arm 68. The chain is tensioned by a spring 98which is connected between the pin 94 and a pin 1110 on the adjacent arm68. Thus, the spring 8 pulls the idler sprocket 92 downwardly againstthe upper flight of the chain 36. The pin 94 passes through a clearanceslot 182 in the arm 65.

The sprocket 94 rotates at the same speed as the shaft 711 and isadapted to drive the impression cylinder 24 when the periodicregistration mechanism 66 forms a positive connection between thesprocket and the cylinder. In this case, the sprocket 913 is formed withthree arms 104 which are arranged in the manner of a spider. A plate ormember 106 is connected to the arms 104 by means of posts or pillars 108which pass through clearance openings 116 in the end plate 78. The plate106 is connected to a central hub or bushing 112 which is rotatablymounted on the shaft 74. It will be evident that the plate 106 rotateswith the sprocket 90.

As shown to advantage in FIG.. 2, the plate 106 is forked and is formedwith two arms or prongs 114 and 116 which straddle a pair of eccentricsor other cams 118 and 1211 which are connected together en-d-toend forcommon rotation about a shaft or pin 122. It will be seen from FIG. 3that the pin 122 is similar to the pillars 84 in that it extends betweenthe end plate 78 and the plate 82. Blocks 124 and 126 are mounted on thearms 114 and 116 for engagement with the eccentrics 118 and 120,respectively. While the illustrated cams are in the form of eccentrics,it will be understood that a variety of other cam shapes may beemployed.

The rotation of the eccentrics 118 and 120 is adapted to provide avariable amount of slack or play between the forked drive plate 106 andthe impression cylinder 24, the slack being variable from zero to amaximum value, according to the position of the eccentrics 118 and 121).In the position shown in FIG. 2, the slack is zero, in that theeccentric 11%; engages the block 124, while the eccentric 12!) engagesthe block 126. This is the point at which positive registration isprovided between the drive sprocket 90 and the impression cylinder 24 sothat the notch 64 in the impression cylinder is accurately andpositively registered with the gripper bar 50. It will be observed thatthe point of maximum throw on the eccentric 118 is engaging the block124, while the point of maximum throw on the eccentric 120 is engagingthe block 126.

When the eccentrics 118 and 120 are rotated, they recede from the block124 and 126 so that there is definite clearance between the blocks andthe eccentrics. This clearance or slack permits the impression cylinder24 to follow the frictional drive of the main cylinder 22.

In this case, the eccentrics 118 and 120 are adapted to be rotated by aplanetary gear 128 which is solidly secured to the eccentrics and isrotatable about the pin or shaft 122. The eccentrics 113 and 120 and thegear 128 may conveniently be molded in one piece from resinous plasticmaterial, preferably a material such as nylon, for example, whichaffords low friction, high strength and great resistance to wear. Theplanetary gear 128 meshes with a pinion 131 which in this case isstationary and is solidly secured to the stationary shaft or trunnion74. It will be,,observed that the pinion 130 is disposed along the axisof the impression cylinder 24 so that the planetary gear 128 rollsaround the pinion when the impression cylinder 24 is rotated. The pinion134) is one-half the size of the planetary gear 128, so that the gear128 rotates at one-half the rotary speed of the impression cylinder 24.Thus, the rotation of the planetary gear 128 produces positiveregistration between the impression cylinder 24 and the drive sprocket90 at one point for every two revolutions of the impression cylinder. Atthis point, the gripper bar 50 is passing between the cylinders 22 and24 and is received in the notch 64. The cycle of the periodicregistration mechanism corresponds to each revolution of the maincylinder 22 which rotates at one-half the rotary speed of the impressioncylinder 24. The cycle of the periodic registration mechanism alsocorresponds to the cycle of the gripper bar 50* which is carried oncearound its complete circuit by the chains 52 for each revolution of themain cylinder 22.

The sprocket and the spider arms 104 may also be conveniently molded inone piece from a resinous plastic material which affords low friction,high strength and great resistance to wear. The hub or bearing 112 mayalso be made of such plastic material.

It may be helpful to summarize the operation of the embodiment shown inFIGS. 1-7. During the operation of the machine, the gripper chains 52are continuously advanced and are effective to produce continuousrotation of the main cylinder 22, due to the meshing of the maincylinder sprocket 58 with one of the chains 52. For each revolution ofthe main cylinder 22, the feed roller 34 engages the topmost copy sheet28 in the stack 30 and propels the sheet past the corner separators 42and between the guide plates 38 and 46 into the nip between theforwarding rollers 44 and 46. The timed rotation of the forwardingrollers 44 and 46 advances the sheet into the grippers 48 on the gripperbar 50, so that the leading end of the sheet is gripped between thegrippers; and the gripper bar. The movement of the gripper bar 50carries the sheet between the main cylinder 22 and the impressioncylinder 24, so that the sheet receives an imprint from the stencil onthe main cylinder 22. The control afforded by the gripper bar 541prevents the sheet from sticking to the main cylinder. The gripper barcarries the sheet beyond the cylinders 22 and 24 until the sheet isdischarged from the grippers and deposited in the receiving tray 62. Theprovision of the grippers 48 and the gripper bar 50 make it unnecessaryto provide strippers to peel the sheet from the main cylinder. In thisway, it is possible to print upon the marginal portions of the sheetwhich are normally left free of any imprint for engagement by the strippers. The grippers also provide accurate and positive registrationbetween the sheet and the stencil on the main cylinder 22.

As the gripper bar 50 passes the impression cylinder 24, the gripper baris received in the notch 64 in the cylinder. During this portion of thecycle, the cylinder 24 is posi tively driven so that it is synchronizedwith the movement of the gripper bar 50. The rotatable eccentrics 118and 121) cooperate with the forked plate 106 to form a positive drivingconnection between the drive sprocket 90, which is positively driven atall times, and the impression cylinder 24. At this point in the cycle,the eccentrics 118 and 126 positively engage the follower blocks 124 and126 on the arms 114 and 116 of the forked plate 106.

' As the cycle of the machine progresses, the rotation of the impressioncylinder 24 causes rotation of the planetary gear 128 which rotates theeccentrics 118 and 120, so that definite slack or clearance is providedbetween the eccentries and the follower blocks 124 and 126. This slackrenders the drive impositive so that the impression cylinder 24 is freeto follow or float with the frictional drive provided by the maincylinder 22 during the passage of the paper sheet between the maincylinder and the impression cylinder. Thus, the impression cylinder doesnot exert any appreciable drag or pull on the stencil, even if theprinting radius of the stencil is slightly greater or less than thenominal value. The maximum slack between eccentrics 118 and 120 and thefollower blocks 124 and 126 is developed'afte-r the eccentrics haverotated through one-half revolution. By this time, the impression roller24 is rotated through one full revolution so that the printing operationhas been completed. The continued rotation of the eccentrics 118 and121i progressively reduces the slack so that a positive drive is again.momentarily provided after the impression cylinder has rotated throughanother revolution. By this time, the gripper bar 50 is again passingbetween the cylinders 22 and 24. The periodic registration mechanisminsures that the notch 64 in the cylinder 24 will accurately registerwith the gripper bar 50.

FIGS. 8-14 illustrate four periodic registration mechanisms of modifiedconstruction. Any of these mechanisms may be substituted for theperiodic registration mechanism 66 of FIGS. 17. In each of the modifiedmechanisms, the variable slack is developed between a cylindrical pin1411 and a tapered notch or slot 142 in a movable member 144. The notch142 is formed by a pair of converging edges or surfaces 146 which areengageable with the pin 140. In each case, the pin 146 is secured to theimpression cylinder 24, while the member 144 is continuously rotated.When the converging surfaces 146 of the notch 142 are fully engaged withthe pin 140, the cylinder 24 is positively driven and is accuratelyregistered with the gripper bar 511. This condition of full registrationoccurs at one point in the cycle of the registration mechanism, when thegripper bar is passing the impression cylinder 24. Throughout theremainder of the cycle, the member 144 is shifted so that the convergingsurfaces 146 are withdrawn to a greater or lesser extent from the pin141). The clearance between the converging surfaces 146 and the pin 140provides slack in the drive so that the impression cylinder 24 is freeto follow the frictional drive of the main cylinder 22.

In the registration mechanism 148 of FIGS. 8 and 9, the member 144 isslidably mounted on a sprocket 150 which is continuously driven by achain 152, corresponding to the chain 86 of FIG. 3. Thus, the sprocket1511 is continuously driven in timed relation to the main cylinder 22and the gripper chains 52. The pin 140 extends through a clearance slot154 in the sprocket 15d.

It will be seen that the sprocket 154 has a hub 156 which is slidablyreceived in an elongated guide slot 158 formed in the member 144. A pin16% is mounted on the member 144 and extends through a guide slot 162 inthe sprocket 156. Thus, the member 144 is slidable laterally along thesprocket 150 so that the relationship between the pin 1411 and thetapered slot 142 may be changed.

This relationship is changed in a periodic manner by an internaleccentric or other cam 164 which is rotatable about a shaft 166, aboutwhich the sprocket 156 is also rotatable. In this case, the cam 164 iscontinuously driven by a chain 168- which is threaded around a sprocket170 formed on or connected to the cam 164. Like the chain 152, the chain163 is synchronized with the main cylinder 22 and the gripper chains 52,but is adapted to drive the sprocket 17 at one-half the rotary speed ofthe sprocket 150, so that the cam 164 will be rotated once for every tworevolutions of the impression cylinder 24.

The member 144 is fitted with a follower roller 172 which may berotatably mounted on the pin 160. Springs 174 are connected between themember 144 and the sprocket 150 to bias the roller 172 against theinternal eccentric or cam 164. Thus, the rotation of the cam 164reciprocates the member 144 on the sprocket 150 so as to move theconverging surfaces 146 into and out of engagement with the pin 140.Full engagement between the surfaces 146 and the pin 140 occurs once forevery two revolutions of the impressions cylinder 24. At this point inthe cycle, the impression cylinder 24 is positively registered with themain cylinder 22 and the gripper bar 50. At other points in the cycle,the registration is impositive so that the impression roller is free tofollow the frictional drive of the main cylinder.

In the modified registration mechanism 180 of FIGS. and 11, the member144 and the sprocket 150 are retained but are changed in shape and willbe designated 144a and 1511a. The member 144a is guided for lateralmovement on the sprocket 150a by guide pins 182, 184 and 186 whichextend through guide slots 188, 190 and .192.

The internal eccentric or cam 164 is also retained but is of differentshape and will be designated 16411. As before, the cam 164a iscontinuously driven at one-half the rotary speed of the sprocket 150a.However, in this case, the cam 164a is fitted with a gear 194 which maybe driven by an idler gear 196 which is synchronized with the rotationof the main cylinder 22 and the movement of the gripper bar 50. Thefollower roller 172 is retained but is arranged differently and isdesignated 172a. In this case, the follower roller 172a is rather largeand is rotatably mounted on a hollow cylindrical journal 198 formed onthe member 144a. Springs 174a are connected between the member 144a andthe sprocket 150a to bias the roller 172a against the cam 164a. In thisway, the converging edges 146 of the V-shaped notch 142 are moved intoand out of engagement with the pin 140 so as to afford a clearance orslack which is substantial during most of the cycle but which becomeszero at the point of positive registration, so that the cylinder 24 willbe accurately registeredwith the gripper bar 51).

In the modified registration mechanism 210 of FIGS. 12 and 13, theinternal cam 164 is replaced with an external cam 16% which isengageable with the follower roller 1721) on the slidable member 1441).In this case, the sprocket 151) is replaced with a 'gear 1519b which iscontinuously driven by an idler gear 212. As shown in FIG. 12, the idlergear 212 is driven by a gear 214 which may be mounted on the shaft whichcarries the gripper sprockets 54. Springs 174% are connected between themember 14% and the gear 15011 to bias the roller ,172b against the cam16412.

The sprocket 170 is replaced with a gear 17Gb which is connected to orformed integrally with the cam 16412. The gear 1711b is driven by anidler gear 216, but at onehalf the rotary speed of the gear 15Gb. Thus,the converging surfaces 146 are moved into positive engagement with thepin for a brief interval during every two revolutions of the impressioncylinder 24. Other corresponding components are given the same referencecharacters as in FIGS. 8 and 9, with the addition of the sufliX b.

FIGS. 14 and 15 illustrate still another modified registration mechanism220, in which the sprocket is replaced with a gear 15110 which may bedriven in the manner shown in FIG. 12. The member 144 is replaced with amodified member 1440 having a pair of arms or fingers 222 which areslidably guided between a pair of spaced blocks or lugs 224 formed onthe gear 150C. The blocks 224 engage the fingers 222 and cause themember 1440 to rotate with the gear 1500.

In this case, the cam 164 is replaced with an eccentric 164c which isformed on a gear e, corresponding to to the sprocket 17 0. The gear 1706may be driven in the manner shown in FIGS. 12 and 13 at one-half therotary speed of the gear 1500.

The member 1440 is fitted with a bushing 226 which is rotatably mountedon the eccentric 164a and is adapted to travel with the ecccentric.Thus, the rotation of the eccentric 1640 causes combined reciprocationand rocking movement of the member 1440, relative to the gear 1500. Inthis way, the converging surfaces 146 on the member 1440 are movedtoward and away from the pin 140. When the surfaces 146 engage the pin140, the impression cylinder 24 is positively driven and is accuratelyregistered with the main cylinder and the gripper chains.

In all of the described embodiments, the periodic registration mechanismis employed to control the registration of the impression cylinder sothat it will be accurately registered at one point in the cycle of themachine. Such registration is normally timed to occur as each of thecopy sheets is fed between the main cylinder and the impressioncylinder. During the remainder of the cycle, the registration becomesimpositive so that the impression cylinder may be frictionally driven bythe copy sheet which is traveling between the impression cylinder andthe main cylinder. However, it will be understood that the presentinvention may be applied to other printing cylinders or members so as toachieve periodic registration.

When applied to the impression cylinder of a stencil duplicator, theperiodic registration insures that the impression cylinder will beregistered with the main cylinder and will be driven at substantiallythe surface speed of the main cylinder when each copy sheet is fedbetween the cylinders. The stencil is never required to accelerate theimpression cylinder to any appreciable extent. Thus, the periodicregistration mechanism obviates the stretching of the stencil which isfrictionally experienced in the usual stencil duplicator having a freerunning impression roller. Such a free running roller is not registeredand is driven solely by frictional engagement with the stencil and themain cylinder. When such a machine is started, or when the speed of themachine is changed abruptly, the stencil is required to accelerate theimpression roller. The force required to produce such acceleration oftentends to stretch the stencil.

The periodic registration mechanism of the present invention has theefifect of registering the impression cylinder and driving it atsubstantially the speed of the main cylinder, at the point in the cyclewhen the head or leading end of the stencil is engaging the leading endof the copy sheet. This is the point in the cycle at which thestretching of the stencil is most apt to occur in a conventional machinehaving a free running impression roller. The periodic registrationmechanism obviates any tendency to stretch the stencil at this point inthe cycle.

The periodic registration mechanism is also superior to a positive drivethat will produce continuously positive registration of the impressioncylinder. With a positive drive, slight differences tend to developbetween the surface speeds of the stencil and the impression cylinder,due to variations in the thickness of the stencil and the ink pad. Thesespeed dilferences tend to cause stretching or wrinkling of the stencil.With the periodic registration, the impression cylinder is positivelyregistered at the beginning of the cycle but thereafter is frictionallydriven by the stencil cylinder so that the surface speed of theimpression cylinder will be exactly the same as the surface speed of thestencil.

Various other modifications, alternative constructions and equivalentsmay be employed without departing from the true sprit and scope of theinvention, as exemplified in the foregoing description and defined inthe following claims.

We claim:

1. In a duplicator, the combination comprising a ro tatable maincylinder for holding a printing member, a rotatable impression cylinderengageable with said main cylinder, a movable gripper bar havinggrippers thereon for carrying successive copy sheets between saidcylinders, a pair of endless chains supporting the opposite ends of saidgripper bar, means for supporting and driving said endless chains, meansfor driving said main cylinder in timed relation to said chains, saidimpression cylinder having a notch therein for receiving said gripperbar to provide for the movement of said gripper bar between saidcylinders, means forming a driving connection between said chains andsaid impression cylinder, means providing a variable play in saiddriving connection, andmeans connected between said chains and said lastmentioned means for reducing said play to a minimum condition when saidgripper bar passes between said cylinders while increasing said playafter passage of said gripper bar therebetween so that said impressioncylinder will be frictionally driven by said main cylinder during theprinting of the copy sheets.

2. In a registration mechanism, the combination comprising a rotatablecylinder, a rotatable drive member adjacent and coaxial with saidcylinder, means for rotating said member, a stationary pinion adjacentand coaxial with said cylinder, a planetary gear rotatably mounted onsaid cylinder for rotation relative thereto and meshing with saidpinion, a pair of opposed arms on said memher, and a pair of eccentriccams connected to said planetary gear and rotatable therewith betweensaid arms to 'form therewith a drive between said drive member and saidcylinder, said drive alfording minimum play between said eccentric camsand said arms at one point in the cycle of said eccentric cams andaffording progressively variable play therebetween during the remainderof such cycle.

3. In a registration mechanism for a printing press, the combinationcomprising a rotatable press member, a rotatable drive member coaxialwith and adjacent said press member, means for rotating said drivemember, a stationary pinion coaxial with said press member, a planetarygear rotatably mounted on said press member and meshing with saidpinion, a pair of spaced elements on said drive member, and rotatablecamming means connected to said planetary gear and rotatable therewithbe tween said elements between a positive registration position in whichsaid carnming means have minimum play with both of said elements and animpositive registration position in which said camming means are recededfrom said elements to provide substantial play between said cammingmeans and said elements, said camming means thereby affording variableplay in the drive of said press member.

4. In a registration mechanism for a printing press, the combinationcomprising a rotatable press member, a rotatable drive member adjacentand coaxial with said press member, means for rotating said drivemember, a pair of spaced driving elements on said drive member andadjacent said press member, camrning means rotatably mounted on saidpress member and disposed between said spaced elements to form therewitha driving connection between said drive member and said press member,and means for rotating said camming means between a position in whichsaid camming means have minimum play with both of said elements and aposition in which said camming means are receded from said elements toafford substantial play between said camming means and said elements.

5. In a registration mechanism for a printing press, the combinationcomprising a rotatable press member, a rotatable driving member adjacentand coaxial with said press member, first and second driving elements onsaid driving and press members and forming a driving connectiontherebetween, and means for moving one of said elements relative to theother element between a position in which said elements are fullyengaged with minimum play therebetween and another position in whichsaid one element is receded from the other element to afford substantialplay therebetween.

6. In a registration mechanism, the combination comprising a rotatablecylinder, a rotatable drive member adjacent and coaxial with saidcylinder, driving means for rotating said drive member, a movableelement mounted on said drive member for movement relative thereto andhaving converging surfaces forming a tapered notch, a drive pin mountedon said cylinder and received in said notch, and camming means operableby said driving means for moving said element between a positiveregistration position in which said converging surfaces engage said pinand an impositive registration position in which said convergingsurfaces are receded from said pin to provide substantial play betweensaid element and said pin.

7. In a registration mechanism for a printing press, the combinationcomprising a rotatable press member, a ro-. tatable driving memberadjacent and coaxial with said press member, first and second drivingelements on said driving and press members and forming a drivingconnection therebetween, one of said elements having con- .vergingsurfaces forming a tapered opening, the other of said elementscomprising a pin received in said tapered opening, and means for movingone of said elements relative to the other element between a positiveregistration position in which said pin and said converging surfaces arefully engaged and an impositive registration position in which said pinis spaced from said converging surfaces to atford substantial playbetween said pin and said converging surfaces.

8. In a registration mechanism, the combination comprising a rotatablepress member, a rotatable driving member adjacent and coaxial with saidpress member, first and second driving elements on said driving andpress members and forming a driving connection therebetween, one of saidelements comprising camming means, the other of said elements comprisingfollower means engageable with said camming means, and means for movingone of said elements relative to the other element between positions ofminimum and maximum spacing between said camming means and said followermeans to afford variable play therebetween.

9. In a duplicator, the combination comprising a rotatable main cylinderfor holding a printing member, a rotatable impression cylinderengageable with said main cylinder, a movable gripper bar havinggrippers thereon for carrying successive copy sheets between saidcylinders, a pair of endless chains supporting the ends of said gripperbar, means for supporting and driving said chains, means for drivingsaid main cylinder in timed relation to said chains, said impressioncylinder having a recess therein for receiving said gripper bar toprovide for the movement of said gripper bar between said cylinders, anda periodic registration mechanism connected between said chains and saidimpression cylinder and including means forming a driving connectionwith variable play therein between said chains and said impressioncylinder, and means connected to said last-mentioned means and opetrablein timed relation to said chains for periodically reducing said play toa minimum value when said gripper bar is passing between said cylindersand thereafter increasing said play to allow for frictional drive ofsaid impression cylinder by said main cylinder during the printing ofthe copy sheets.

10. In a duplicator, the combination comprising a rotatable maincylinder for holding a printing mem- 12 ber, a rot atableimpressioncylinder engageable with said main cylinder, a movable gripper barhaving grippers thereon for carrying successive copy sheet-s betweensaid cylinders, a pair of endless chains supporting the ends of saidgripper bars, means for supporting and driving said chains, means fordriving said main cylinder in timed relation to said chains, saidimpression cylinder having a recess therein for receiving said gripperbar to provide for the movement of said gripper bar between saidcylinders, a rotatable drive member adjacent said impression cylinder,means for driving said drive member in timed relation to said chains,first and second driving elements on said drive member and saidimpression cylinder and forming a driving connection therebetween, oneof said elements being movable relative to the other of said elements tovary the play therebe'tween, and means operable in timed relation tosaid chains for moving said one element to reduce said play to a minimumvalue when said gripper bar is passing between said cylinders andthereafter to increase said play to allow for frictional drive of saidimpression cylinder b-y said main cylinder during the printing of thecopy sheets.

11. The combination of claim 10, in which one of said driving elementscomprises a pair of converging surfaces forming a tapered opening andthe other of said driving elements comprises a pin received in saidtapered opening.

12. The combination of claim 10, in which one of said driving elementscomprises rotatable camming means, and the other of said drivingelements comprises a pair of spaced followers on opposite sides of saidcamming means with variable play between said followers and said cammingmeans, said camming means being rotatable in timed relation to saidchains.

References Cited by the Examiner UNITED STATES PATENTS 1,867,529 7/1932Jones 101-248 2,406,205 8/1946 Davidson et al 101-232 2,551,060 5/1951Simmons 101-232 2,794,390 6/1957 Burke 101-232 2,887,046 5/1959 Knops etal 101248 ROBERT E. PULFREY, Primary Examiner.

P. R. WOODS, Assistant Examiner.

5. IN A REGISTRATION MECHANISM FOR A PRINTING PRESS, THE COMBINATIONCOMPRISING A ROTATABLE PRESS MEMBER, A ROTATABLE DRIVING MEMBER ADJACENTAND COAXIAL WITH SAID PRESS MEMBER, FIRST AND SECOND DRIVING ELEMENTS ONSAID DRIVING AND PRESS MEMBERS AND FORMING A DRIVING CONNECTIONTHEREBETWEEN, AND MEANS FOR MOVING ONE OF SAID ELEMENTS RELATIVE TO THEOTHER ELEMENT BETWEEN A POSITION IN WHICH SAID ELEMENTS ARE FULLYENGAGED WITH MINUMUM PLAY THEREBETWEEN AND ANOTHER POSITION IN WHICHSAID ONE ELEMENT IS RECEDED FROM THE OTHER ELEMENT TO AFFORD SUBSTANTIALPLAY THEREBETWEEN.